SUPERTWIST LIQUID-CRYSTAL DISPLAY

Abstract: The invention relates to improved STN displays of which the nematic liquid crystalline medium comprises compounds of formulae: (I1, I2, II1 and/or III1). In formulae (I1 and I2) R<3> and R<4> are each independently alkyl with 1 to 8 C atoms. In formula (II1) R<1> is alkyl or alkoxy with 1 to 8 C atoms, and in formula (III1) R<2> is oxaalkyl, alkenyl with up to 8 C atoms.

Description: Supert ist liquid-crystal display The invention relates to supertwist liquid-crystal displays (STN displays) having extremely short switching times and good steepnesses and angle dependencies, and to the novel nematic liquid-crystal mixtures used therein. STN displays as in the heading are known, for example from EP 0,131 ,216 B1 ; DE 3,423,993 A1 ; EP 0,098,070 A2; M. Schadt and F. Leenhouts, 17th Freiburg conference on liquid crystals (8-10.04.87); K. Kawasaki et al., SID 87 Digest 391 (20.6); M. Schadt and F. Leenhouts, SID 87 Digest 372 (20.1 ); K. Katoh et al., Japanese Journal of Applied Physics, Vol. 26, No. 11 , L 1784-L1786 (1987); F. Leenhouts et al., Appl. Phys. Lett. 5 (21), 1468 (1987); H.A. van Sprang and H.G. Koopman, J. Appl. Phys. £2 (5), 1734 (1987); T . Scheffer and J. Nehring, Appl. Phys. Lett. 4$ (10), 1021 (1984), M. Schadt and F. Leenhouts, Appl. Phys. Lett. 50 (5), 236 (1987) and E.P. Raynes, Mol. Cryst. Liq. Cryst. Letters, Vol. 4 (1 ), pp. 1-8 (1986). The term SFA here includes any relatively highly twisted display element having a twist angle with a value between 160 ° and 720 °, such as, for example, the display elements of Waters et al. (CM. Waters et al., Proc. Soc. Inf. Disp. (New York) (1985) (3rd Intern. Display Conference, Kobe, Japan), the STN-LCDs (DE OS 3,503,259), SBE-LCDs (T.J. Scheffer and J. Nehring, Appl. Phys. Lett. 45 (1984) 1021 ), OMI-LCDs (M. Schadt andF. Leenhouts, Appl. Phys. Lett. 50 (1987), 236, DST-LCDs (EP OS 0,246,842) or BW-STN-LCDs (K. Kawasaki et al., SID 87 Digest 391 (20.6)). Compared with standard TN displays, STN displays of this type are distinguished by significantly better steepnesses of the electrooptical characteristic and, associated therewith, better contrast values, and by a significantly lower angle dependence of the contrast. Of particular interest are STN displays with extremely short switching times, in particular also at relatively low temperatures. In order to achieve short switching times.the viscosities, in particular of the liquid crystal mixtures have hitherto been optimized using usually optimized combinations of liquid crystal components and optionally also monotropic additives of relatively high vapour pressure. However, the switching times achieved were not adequate for all applications. Shorter switching times can also be achieved by reducing the thickness of LC layer of the STN display and using liquid-crystal mixtures with a higher birefringence Δn. All these approaches to shorter switching times, however, still end up with mixtures which were not adequate for every use. The European patent EP 0 366 985 describes STN displays with comparable short switching times with 180° twist based on 4-alkyl-4'- alkoxybicyclohexyles. There is still a demand to improve these switching times. Further demands for STN display are a higher multiplexability, lower threshold voltages and a steep characteristic curve. Optimal parameters, however, cannot be achieved simultaneously for all the properties mentioned above because of opposite influence of different material parameters such as dielectric and elastic properties. Therefore, there continues to be a great demand for improved STN displays having short switching times and, at the same time, a broad service temperature range, high characteristic line steepness, good angle dependency of the contrast and low threshold voltage. The invention has the object of providing STN displays which only have the abovementioned disadvantages to a small extent, or not at all, and at the same time have very useful overall properties. It has now been found that this object can be achieved if nematic liquid- crystal mixtures are used which contain one or more compounds selected from the formulae 11 , 12, 111 and II2 wherein R3 and R4 are each independently alkyl with 1 to 8 C atoms, wherein R is alkyl or alkoxy with 1 to 8 C atoms, wherein Rs is oxaalkyl, alkenyl with up to 8 C atoms. The nematic liquid-crystal mixture preferably has a nematic phase range of at least 60 °C, a viscosity of not more than 35 mPa.s and a dielectric anisotropy of at least +1 , the dielectric anisotropies of the compounds and the parameters related to the nematic liquid-crystal mixture being based on a temperature of 20 °C. The invention thus relates to a STN display having two plane-parallel outer plates which, together with a frame, form a cell, - a nematic liquid-crystal mixture of positive dielectric anisotropy which is present in the cell, electrode layers with superposed alignment layers on the insides of the outer plates, a pre-tilt angle between the longitudinal axis of the molecules at the surface of the outer plates and the outer plates of from about 1 degree to 30 degrees, and a twist angle of the liquid-crystal mixture in the cell from alignment layer to alignment layer with a value of between 100 and 600°, wherein the nematic liquid-crystal mixture a) comprises 20-90 % by weight of a liquid-crystalline componeηt A. comprising one or more compounds having a dielectric anisotropy of more than +1.5; b) comprises 10-65 % by weight of a liquid-crystalline component B. comprising one or more components having a dielectric anisotropy from -1.5 to +1.5; c) comprises 0-20 % by weight of a liquid-crystalline component C. comprising one or more compounds having a dielectric anisotropy of below -1.5, and d) comprises an optically active component D in such an amount that the ratio between the layer thickness (separation of the plane- parallel outer plates) and the natural pitch of the chiral nematic liquid-crystal mixture is from about 0.2 to 1.3 and the nematic liquid-crystal mixture has a nematic phase range of at least 60 °C, a viscosity of not more than 35 mPa.s and a dielectric anisotropy of at least +1 , the dielectric anisotropies of the compounds and the parameters based on the nematic liquid-crystal mixture being based on a temperature of 20 °C, characterized in that component B comprises at least one compound of formulae 11 and/or 12: wherein R3 and R 4 are each independently alkyl with 1 to 8 C atoms, and/or the component A comprises at least one compound of formulae 111 and/or 1111 wherein Ri is alkyl or alkoxy with 1 to 8 C atoms, wherein R2 is oxaalkyl, alkenyl with up to 8 C atoms. Preferably component B comprises at least one compound of formula 11 and/or 12 and component A contains compounds of the formulae II and I wherein R is alkyl, alkoxy, oxaalkyi alkenyl or alkenyloxy with up to 12 C atoms, - A}-, — < >— an d are each indepedently V through Le are each independently H or F, Zi is -COO-, -CH 2 CH 2 - or a single bond, 7 Z2 is -COO-, -CH 2 CH 2 -, -C≡C or a single bond, Q is CF 2 , OCF 2 , CFH, OCFH or a single bond, is F or CI, is 1 or 2, and n is 0 or 1 , in particular selected from the formulae lla to lid and/or lla to lllh: wherein R, Li, L3 and Q have the meaning given. Preferably that component B contains one or more compounds selected from the group comprising IV to V: in which Rs and R β have the meaning given for R and ~ Λ / ~ , ~" _y _ ' L ' have the meaning given for formulae II or III, and Za is -COO-, -CH 2 CH 2 -, -CH=CH- or a single bond, Z 4 is -COO- or a single bond. In a particularly preferred embodiment component B contains at least one compound of formula 11 and at least one compound of formula V1 : i 0 wherein Rs and Re are each independently alkyl with 1 to 8 C atoms, L° is H or F, and k and I are each independently 0 or 1 , in particular in which L° is F, k is 1 , and n is 0, and/or at least one compound of formula V1 , in which L° is H, k is 0, and n is O oM . Preferably component B contains one or more compounds of formula 11a: wherein o and p each are integers between 0 and 7 and the sum of o + p is an integer between 1 and 7. The invention also relates to the corresponding liquid-crystal mixtures. Another aspect of the invention is the use of compounds of formulae 11 , 12, 111 and/ 1111 , wherein Ri, R2, R3 and R 4 have the meaning given for the improvement of the switching times and/or the electro-optic steepness of STN-dispIays, and The compounds of formulae 11 , 12, 111 and 1111 are partly known and partly novel. The invention therefore relates to these novel compounds, which are the following: a) Compounds of formula I2a, wherein the sum of q + v is 0 or 1 ; b) 2'-Fluoro-4-cyano biphenyl of formula 111 a wherein Qi is O, CH 2 or a single bond. Another aspect of the invention is the use of a composition of at least two compounds of formulae 11 and 12 wherein R', R2, Lo, K, and I have the meaning given for the improvement of the switching times of STN-displays. The invention relates furthermore to an improved process for the preparation of 2'-fluoro-4-cyano biphenyls of formula I, the improvement wherein is that a 2-fluorophenylboronic acid of formula A, wherein Ri has the meaning given is reacted with a p-halogen benzonitrile of formula B, wherein Hal is Cl or Br, in the presence of catalytic amounts of a transition metal which is bonded to a phosphin ligand. The individual compounds of the formulae 11 , 12, II, 111 , III and 1111 and also other compounds which can be used in the STN displays according to the invention, are either known or can be prepared analogously to the known compounds. The compounds of formula 11 are known from Japanese laid open application JP 60-1857-A; the compounds of formula 11 are partly known from DE 29 277277; the compounds of formula 111 are partly known from J.E. Fearon et. al Mol. Cryst. Liq. Cryst. 1985, Vol. 124 pp. 89-103; compounds of formula 1111 are known from DE 37 32 284, and the compounds of formula V1 are known from German laid open application DE 2933563 and DE 3211306, but there is no hint in these publications that the steepness and the switching times of SFA's can be improved with the aid of these compounds. The mixtures of this invention allow the realization of STN displays with high multiplex ratios, broad working temperature range, low threshold voltages (below 3 volt, preferably between 1.25 and 2.80, in particular between 1.60 and 2.20 volt) and steep characteristic curves. The compounds of the formulae 11 , 12, 111 and 1111 impart to improved STN compositions, in particular with higher clearing points; the compounds of formula 11 and II2 have low values of the rotational viscosity and lead therefore to short switching times; the compounds of formulae 12 and 1111 have high values of the ratio of the elastic constants (K 3 /K and lead thereofore to high steepnesses. The mixtures according to the present invention have an optic anisotropy (Δn) of more than 0.120, preferably 0.130-0.170, in particular 0.130-0.160. The mixtures according to the invention preferably contain one or more compounds of formula III with three rings selected from the following group: R-( H )— < H -CH 2 CH 2 — - O )-OCHF 2 Hld5 R- H )-CH 2 CH 2 — < H { O >— F Hig-i Preferred mixtures contain two, three or more compounds of the formulae 11 , 12, 111 , 1111 , lla, lib, lie, lid, lllb and lllc, in particular one or more compounds of the formula lllb and two to four compounds of formulae 11/12 and one to three compounds selected from the formulae lib and lie. Preferred liquid-crystal mixtures which can be used according to the invention contain one or more compounds from ςiroup A preferably in a proportion of 20 % to 90 %, preferably 35 % to 80 %. These compounds or this compound from group A have a dielectric anisotropy of more than +8 (preferably of more than +12) and form the component A of the LC mixtures of this invention. Preferably group A comprises additionally compounds selected from the following group: R has the meaning given, F Qi is the formula — - ( ~ - , —fo — or —( — Z i is — ~ -, - ~ VCH 2 CH 2 -, a single bond, -CH 2 CH 2 , -CO-O- or -O-CO- and A V- is — ( \ — or — ( O Preferably the mixtures comprise one ore more compounds of the formula Al in the range of 5 to 50 %. Preferred are those compounds wherein Zi denotes a single bond, -CH 2 CH 2 - or -CO-O- and especially preferred are the following compounds: Also preferred are the following compounds: Group A preferably comprises one ore more compounds selected from the formulae 111 , 1111 , Ilb1 to lid and optionally also one or more compounds of the formula Ilc2. Preferably the mixtures further contain one or more polar compounds with a higher clearing point, e.g. selected from the following compounds: 18 In the above four formulae the 1 ,4-phenylene rings can also be laterally substituted by one fluorine atom, e.g. R- H — < H >— < O >-CN Hg1 These polar compounds with a higher clearing point are preferably used in the range of 2 to 25 %. In another preferred embodiment the mixtures comprise one or more compounds with a very high dielectric anisotropy. Such compounds are preferably used in the range of 2 to 50 %. Preferred compounds of this type are those of the formulael, Ilc2 and Ilj1. Preferred liquid-crystal mixtures contain two or more compounds from group B. preferably in a proportion of 10 % to 40 %. These compounds or this compound from group B have either low values of the rotational viscosity (γi) < 150 mPa-s or a clearing point of more than 120 ° and are dielectrically neutral ((Δε) < 2) or medium polar (Δε in the range of +2 to +10, preferably +4 to +8) and form component B of the LC mixtures of this invention. Preferablv component B contains in addition to the compounds of formulae 11 and 12 preferably one or more compounds selected from the group comprising IV1 to IV8 with two rings: in which Rs and Re have the meaning given for R and/or one or more compounds selected from the group comprising IV9 to IV25 with three rings: * 5 -^ H Λ 0 λΛ H >- R6 ,V9 in which Rs and R 6 have the meaning given, the 1 ,4-phenylene groups IV9 to IV18 and IV22 and IV23 may each, independently of one another, also be mono- or polysubstituted by fluorine, and/or one or more compounds selected from the group comprising IV26 to IV31 : R 5 -^H^CH 2 CH 2 — ^^ 'V27 R 5 - H H O H V-R 6 ' 8 in which Rs and Re have the meaning given, and the 1 ,4-phenylene groups in IV26 to IV31 may each, independently of one another, also be mono- or polysubstituted by fluorine. The LC mixtures also comprise an optically active component C, in an amount such that the ratio between the layer thickness (separation of the plane-parallel carrier plates) and the natural pitch of the chiral nematic liquid crystal mixture is more than 0.2 suitable to the desired twist angle. Suitable dopants can be selected from a wide variety of known chiral materials and commercially available dopants such as cholesteryl nonanoate, S 811 (E. Merck, Darmstadt, FRG) and CB 15 (BDH, Poole, UK). The choice thereof is not crucial per se. Preferably the mixtures also contain one or more compounds from group HI comprising the compounds of the formulae B1 I to B1 IV: 24 in which Rs and Re, in each case independently of one another, are as J 0 defined for R, Z2 is -CH 2 CH 2 -, -CO-O-, -O-CO- or a single bond, and J 5 and/or at least one component selected from group B2 comprising the compounds of the formulae B1V to B1VII: in which Rs is as defined for R, 30 Zo is -CH 2 CH 2 - or a single bond, and 35 where n is 1 to 9, X is CN or F and Y is H or F; and/or at least one component selected from group B3 comprising the compounds of the formulae BVIII, BIX and BX: BVIII in which Rs and Re, in each case independently of one another, are as defined for R, X is Cl or F, and preferably In a further preferred embodiment the LC mixtures contain one or more, compounds selected from group T. comprising compounds of the formulae Tl and T2: R 9 — ( D V-Z°— O > — C≡≡C-Q 3 T2 or — ° — ■ preferably L3 to Le, Q and Y are as defined for the compounds of the formula III. R9 and Ri° , in each case independently of one another, are each R, X is F, Cl or OCF 3 , and Zo is -COO-, -CH 2 CH 2 - or a single bond. The proportion of component(s) from group T is preferably 5 % to 30 %, in particular 5 % to 20 %. Preferably component B contains one or more compounds selected from the group comprising X to XII: ≡C-{ o >-R 10 XM in which Rs and Rw have the meaning given, in particular wherein R2 is alkyl with 1 to 4, most preferred 1 or 2 C-atoms and R3 is alkoxy with 1 to 4, most preferred 1 or 2 C-atoms. The proportion of component(s) from group B1 is preferably 10 % to 50 %, in particular preferably about 15 % to 40 %. Components of the formulae B1 III and B1 IV are preferred. Particularly preferred compounds of the formula B1 III are those of the following sub-formulae: in which Rn is CH 3 -(CH 2 ) n -0-, trans-H-(CH 2 ) r -CH=CH-(CH 2 CH 2 ) s -CH 2 0- or trans-H-(CH 2 ) f -CH=CH-(CH 2 CH 2 ) s -, R12 is CH 3 -(CH 2 ) r , in particular in which R2 is CH 3 -(CH 2 ) n -0- with n being an integer between 0 and 4 and t being an integer between 0 and 4, n is 0 to 8 t is 0 to 8. Furthermore preferred compounds are those of the sub-formula in which Rn and R12 are as defined above. The proportion of the compounds of the formula B1 III of the above men¬ tioned sub-formulae is preferably about 5 % to 45 %, in particular preferably about 10 % to 35 %. Particularly preferred compounds of the formula B1 IV are those of the following sub-formula: in which 0 R 13 is CH 3 -(CH 2 ) n -0- or trans-H-(CH 2 ) r -CH=CH-(CH 2 CH 2 ) s -CH 2 0- and R1 4 is CH 3 -(CH 2 ),-, where The proportion of these compounds or of the compounds of the formula B1 IV is preferably about 5 % to 40 %, in particular preferably about 10 % to 35 %. 5 In a particularly preferred embodiment, the mixtures simultaneously contain compounds of the formulae B1 III and B1 IV, the total proportion for components of group B1 being observed. 0 If compounds of the formulae B11 and B1 III are present, Rs and Re are preferably, in each case independently of one another, n-alkyl having 1 to 7 C atoms or (trans)-n-alkenyl having 3 to 7 C atoms. Z2 is preferably a single bond. Bl is particularly preferred. 5 Furthermore preferred mixtures according to the invention are those which contain one or more compounds of the formula B1 IV in which - — is —Q>— is — - ' and 5 and 6 have one °f the above mentioned preferred meanings, in particular preferably n-alkyl having 1 to 7 C atoms. In all cases, the total proportion for components of group B1 is observed. The proportion of the compounds of group B2 is preferably about 10 % to 45 %, in particular preferably 10 % to 20 %. The proportion (preferred ranges) for B1V to B1 VII is as follows: B1 V about 10 % to 30 %, preferably about 10 % to 15 % Total of B1 VI and B1 VILabout 10 % to 25 %, preferably about 10 % to 20 %. Preferred compounds of group B2 are indicated below: - 30 Rs is preferably n-alkyl having 1 to 7 C atoms or (trans)-n-alkenyl having 3 to 7 C atoms. Z° is preferably a single bond. Re preferably has the preferred meaning mentioned above for R or is fluorine. Y is preferably • j Q fluorine. The mixtures according to the invention preferably contain one or more compounds selected from the group comprising B1 V3, B1 VI1 and B1 VII1 in a total proportion of about 10 to 35 %. 15 In a particularly preferred embodiment, the mixtures according to the invention contain, besides B1V3, B1VI1 , B1VII1 and B1V2 (R = F), further terminally fluorinated compounds, for example selected from the group comprising: 35 in which R is preferably n-alkyl having 1 to 7 C atoms or (trans)-nalkenyl having 3 to 7 C atoms, X is 1 or 2, y is 0 or 1 and Y is H or F. The total proportion of all terminally fluorinated compounds is preferably about 5 % to 65 %, in particular about 15 % to 40 %. The proportion of the compounds from group B3 is preferably about 10 % to 30 %, in particular preferably about 10 % to 20 %. R2 is preferably n- alkyl or n-alkoxy, each having 1 to 9 C atoms. However, it is also possible to employ analogous compounds containing alkenyl or alkenyloxy groups. Compounds of the formula BVIII are preferred. The mixtures according to the invention contain preferably compounds of the formulae 11 and/or 12 and compounds from at least one of groups B1 , B2 and B3. They preferably contain one or more compounds from B1 and one or more compounds from group B2 and/or B3. Mixtures according to the invention containing at least one compound of formula 11 and at least two compounds of formula 12 are particularly preferred. The proportion of compounds of formulae 11 and 12 is preferably about 10 % to 45 %, in particular 15 % to 40 %. The proportion of compounds of formula 11 is preferably 5 % to 20 %, in particular 8 % to 18 %. The proportion of the compounds of formula 12 is preferably 2 % to 30 %, in particular 5 to 25 %. The proportion of compounds of component C is preferably about 0 % to 20 %, in particular about 0 % to 10 %. Those skilled in the art can easily adjust this proportion to produce the threshold voltage desired, it being possible to use, in principle, all customary liquid-crystal compounds where Δε < -1.5. In a particularly preferred embodiment, the mixtures according to the invention preferably contain about 5 % to 20 % of one or more compounds having a dielectric anisotropy of less than -2 (component C). Compounds of this type are known, for example derivatives of 2,3- dicyanohydroquinone orcyclohexane derivatives containing the structural element as DE-OS 3,231 ,707 or DE-OS 3,407,013. However, compounds containing the structural element 2,3-difluoro-1 ,4- phenylene are preferably chosen, for example compounds as in DE-OS 3,807,801 , 3,807,861 , 3,807,863, 3,807,864 or 3,807,908. Particularly preferred are tolans containing these structural elements, as in Intemational Patent Application PCT/DE 88/00133, in particular those of the formulae 33 - in which Ris and R 6 , in each case independently of one another, are preferably n-alkyl having 1 to 7 C atoms or n-alkenyl having 3 to 7 C atoms, and Z<> is -CH 2 CH 2 - or a single bond. Particularly preferred are also the phenylcyelohexylearboxylates of the formulae Display according to at least one of Claims 1 to 6, characterized in that component C contains one or more compounds selected from the group comprising V to IX: I o in which R and Rs have the meaning given and s is 0 or 1. Preferablv component B contains one or more compounds selected from the group comprising Xato Xlla: 5 in which alkyl and alkoxy denote alkyl or alkoxy with 1 to 7 C atoms. Component C causes, in particular, an improvement in the steepness of the characteristic line. 0 In a particularly preferred embodiment, the mixtures contain about 5 % to 35 %, in particular preferably about 10 % to 20 %, of liquid-crystalline tolan compounds. These make it possible to work with smaller cell thicknesses (about 5-6 μm), which significantly shorten the switching times. Particularly preferred tolans are indicated below: 5 Ra is preferably n-alkyl having 1 to 7 C atoms, Zo is -CH 2 CH 2 - or a single bond, —2>— is — ^ ~ or —ζ° ~ preferably — TN— , Q3 is ~ (D"" 1*1 ~ °V F • ° r — (° ~∞F ' where Rio is n-alkyl or n-alkoxy, each having 1 to 7 C atoms, or n-alkenyl or n-alkenyloxy, each having 3 to 7 C atoms. Preferably component A contains one or more compounds of the formula T3a in which Rn iS-C nH2n+ ι,-OC n H 2n+1 , n is an integer from 1 to 15, L3 to Le are each, independently of one another, H or F, and X is F, Cl or OCF 3 . In a preferred embodiment the nematic mixture contains 5-25 % of one or more compounds of formula 11 , 20-35 % of two or more compounds selected from the formulae X, XI, XII and T1 b, and 10-30 % of two or more compounds of formula lla. These mixtures show very short switching times of less than 100 ms, a steepness of 1.07 to 1.15, a birefringence between 0.160 to 0.180 and a threshold voltage between 2.0 and 2.5 Volts. These mixtures are in particular suitable for high-multiplexed STN-displays in which each pixel is addressed by orthogonal row wave forms (e.g. Active AddressingTM, τ.H. Scheffer et al.; Displays, Vol 14 (2) 1993, pp. 74-83). In further particularly preferred embodiments, the mixtures contain a component C which contains one or more compounds having a 1-cyano-trans-1 ,4-cyclohexylene group or a 2,3-difluoro-1 ,4- phenylene group, at least two compounds of the formulae Alll or AV, compounds of the formulae Alll and AV, at least one compound from the following group: Alkyl F in which alkyl is a straight-chain alkyl group having 2-7 C atoms, and X is H or F, one or more compounds in which R is a trans-alkenyl group or a trans-alkenyloxy group, one or more compounds selected from the following group in which R5 and R6 have the preferred meanings indicated in the case of component B, and one of the two 1 ,4-phenyIene groups may also be substituted by fluorine; the proportion of these compounds is 0 % to 25 %, preferably about 5 % to 15 %. In a further particularly preferred embodiment the mixtures contain one or more, in particular 1 , 2, 3 or 4, compounds selected from the formulae Hid, lllb, llli and Hip at least two compounds selected from the formulae llbl , Hd or Ilc2. one or more compounds of the formula B1 IV one or more compounds of the formulae T1 or T2 or one or more compounds selected from the following group 39 - wherein R and R are defined as for the compounds of the formula III. J Q As a rule component B consists of 3 to 10, preferably 4 to 9 different compounds. In a preferred embodiment component B essentially consists of: 1 5 at least one compound of formulae 11 and/or 12, and at least one compound selected from the formulae IV2, IV6, IV8, IV11 , IV14, IV17, IV23, IV26, IV31., V1 , B VIII, X and XI, in particular selected from the following formuae: ECCP-nm alkyl PCH-nOm alkyl PTP-nOm alkyl CPTP-nOm 35 alkyl- O alkyl CCP-nm s ailkkvyil D-nOm alkyl - O >— < O V- alkyl CBC-nm alkyl CBC-nmF Component B consists preferably of 3 to 10 compounds, in particular of 5- 60 %, in particular 15-55 % of one, two or three compounds of formula 11 , and/or 10-40 %, in particular 15-30 % of one, two or three compounds of formula 12, and - 41 - 0-45 %, in particular 5-30 % of at least one ECCP-nm; 0-60 %, in particular 10-50 % of at least one PCH-nOm; 0-25 %, in particular 1 -20 % of at least one PTP-nOm; 0-70 %, in particular 15-60 % of at least one CPTP-nOm; 0-20 %, in particular 1 -15 % of at least one BCH-nm; 0-15 %, in particular 5-10 % of at least one CCP-nm; 0-40 %, in particular 5-30 % of at least one CP-nmF; 0-20 %, in particular 1 to 15 % of at least one compounds selected from D-nOm and CP-nm; 0-20 %, in particular 3-17 % of at lest one, preferably one, two PYP-nm; 0-20 %, in particular 5-16 % of at least one, preferably one, two or three compounds selected from CBC-nm, CBC-nmF and CCPCnm. As a rule component A consists of 2 to 9, preferably 4 to 7 compounds. In a preferred embodiment component A essentially consists of at least one compound selected from the formulae 111 , 1111 , lla, lib, He, llh, Hj, lllb, lllc, with Q being OCF 2 , Hldm with Q being a single bond, lllh, with Q being a single bond, lllf, with Q being OCF 2l and T1b, in particular selected from the following formulae: B-nO.FN alkyl O- O O > — ( O V-CN alkyl- O CN PCH-n alkyl - O ) — ( O >-CN K 3n alkyl — ( O V-COO — ( 0 )—C MenN alkyl- O V- COO — ( o CN ME-nN.F CCP-nOCF 3 alkyl CP-nOCF 3 alkyl PTP-nOF Component A consists preferably of 20-100 %, in particular 25-80 % of at least one compound selected from PCH-n and K3n; 0- 40 %, in particular 15-25 % of at least one compound of formulae B- nO.FN; 10- 60 %, in particular 15-40 % of at least one compound selected from CCP-nOCF 3 and CP-nOCF 3 ; 0- 25 %, in particular 5 to 25 % of at least one compound selected from CCP-nV-OT and CCP-nE30CF 3 ; 0- 50 %, in particular 5-30 % of at least one compound selected from MenN, ME-nN.F and HP-nN-F; 0- 30 %, in particular 5-25 % of at least one PTP-nOF; 0- 50 %, in particular 10-25 % of at least one CPTP-nOCF 3 ; 0- 30 %, in particular 5-25 % of at least one PYP-nF; 0- 60 %, in particular 10-25 % of at least one compound selected from BCH-nF.F, ECCP-nF.F and ECCP-nF; and 0- 20 %, in particular 5-15 % of at least one ECCP-n. Preferably the component B contains at least one compound of formula 11 and at least one tolan derivative, in particular 2 to 0.5 parts of formula 11 related to 1 part of tolans. In a preferred embodiment component B essentially consists of 5- 60 %, in particular 15-55 % of at least one compound of formula 11 ; 0- 20 %, in particular 5-18 % of at least one PTP-nOm; 1 - 70 %, in particular 15-60 % of at least one CPTP-nOm, and 0- 60 %, in particular 5-30 % of at least one compound selected from the other neutral compounds, in particular from PCH-nOm, BCH-nOm and CP-nmF. The construction of the liquid-crystal display elements according to the invention from polarizers, electrode base plates and electrodes having a surface treatment such that the preferential orientation (director) of the liquid-crystal molecules in each case adjacent thereto is usually mutually twisted from one electrode to the other by a value of 160 ° to 720 °, corresponds to the customary construction for display elements of this type. Displays having an twist angle between 220° and 270° are preferred. The term customary construction here is used in broad terms and also includes all derivatives and modifications of supertwist cells, in particular also matrix display elements. The surface tilt angle at the two support plates may be identical or different. Identical tilt angles are preferred. An essential difference between the display elements accordding to the invention and the display elements customary hitherto based on the twisted nematic cell is, however, the choice of liquid-crystal components in the liquid-crystal layer. The liquid-crystal mixtures which can be used according to the invention are prepared in a manner customary per se. In general, the desired amount of the components used in a relatively small amount is dissolved in the components making up the principal constituent, expediently at elevated temperature. It is also possible to mix solutions of the components in an organic solvent, for example in acetone, chloroform or methanol, and to remove the solvent again, after mixing, for example by distillation. The dielectrics may also contain further additives known to those skilled in the art and described in the literature. For example, 0-15 % of pleochroic dyes may be added. Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preferred specific embodiments are, therefore, to construed as merely illustrative, and not limitative of the disclosure in any way whatsoever. The entire disclosures of all applications, patent, and publications cited above and below, and of the following corresponding European patent applications are hereby incorporated by reference: The examples below are intended to illustrate the invention, without representing a limitation. The abbreviations have the following meanings: S-N smectic-nematic phase transition temperature, N-l nematic-isotrop phase transition temperature, c.p. clear point, vise. viscosity (m Pa.s), ' awe average switching time = Ton time from switching on until 90 % of the maximum contrast is reached, T 0ff time from switching off until 10 % of the maximum contrast is reached, V 10 threshold voltage (volt) V 90 saturation voltage V90Λ 0 steepness The SFA is addressed in multiplex operation (multiplex ratio 1 :240, bias 1 :15). Above and below, all temperatures are given in °C. Percentages are per cent by weight. The values for the switching times and viscosities relate to 20 °C. In the present patent application and in the following examples all chemical structures of LC compounds are given by acronyms the transformation of which into chemical formulae is done as shown in the following. All residues CnH^ and CmHar,^ are straight-chained alkyl groups with n resp. m carbon atoms. The code of Table B is self- explanatory. In Table A only the acronym for the core structure is given. In a concrete compound this acronym is followed by a dash and a code for the substituents R . R2, Li and L as follows: -48- PYP PYRP BCH CBC CCH CCP CP CPTP CEPTP D ECCP CECP EPCH HP ME PCH PDX PTP BECH EBCH CPC EHP BEP ET Tabelle B: T15 K3n M3n BCH-n.Fm Inm Cnm S-811 C15 CB15 CBC-nmF G3n C n H 2l 1 -^? -^^ CCEPC-nm CCPC-nm CH-nm Example 1 A STN display with the following parameters: contains a liquid crystalline medium with the following properties: S-N < -30° N-l +84° Δn 0.1393 consisting of an aehiral base mixture: PCH-3 22.00 ME2N.F 3.00 ME3N.F 3.00 ME5N.F 5.00 ME5N.F 6.00 CCH-34 20.00 CCP-20CF3 4.00 CCP-30CF3 3.00 CCP-40CF3 3.00 CPTP-301 5.00 CPTP-302 5.00 CPTP-303 4.00 ECCP-31 4.00 ECCP-32 4.00 ECCP-33 4.00 PTP-20F 7.00 - 5< and being doped with 0.61 % of shows the following switching parameters: Ta« 233 ms V 10 1.77 V Vgo/V 10 1.085 Example 2 A STN display as described in Example 1 containing a liquid crystalline medium with the following parameters: N-l +83 °C Δn 0.1407 consisting of an aehiral base mixture: PCH-3 22.00 ME2N.F 7.00 ME3N.F 7.00 ME5N.F 3.00 CCH-34 20.00 CCP-20CF3 7.00 CCP-30CF3 5.00 CPTP-303 7.00 CPTP-302 8.00 ECCP-32 4.00 ECCP-33 3.00 PTP-20F 7.00 being doped with 0.61 % of S-81 1 shows the following switching parameters: V 10 1.67 V Example 3 A STN display as described in Example 1 containing a liquid crystalline medium with the following properties: S-N < +20° N-l +85° Δn 0.1412 γ rot 113 consisting of an aehiral base mixture: being doped with 0.61 % of S-811 shows the following switching parameters: T^ 243 ms V 10 1.82 V Example 4 A STN display as described in Example 1 containing a liquid crystalline medium with the following properties: S-N < -30° N-l +91° Δn 0.1432 consisting of an aehiral base mixture: and being doped with 0.82 % of S-811 shows the following switching parameters: T 267 ms V 10 1.73 V VgoΛ ,0 1.072 Example 5 A STN display as described in Example 1 containing a liquid crystalline medium with the following properties: S-N < -30° N-l +88° Δn 0.1408 consisting of an aehiral base mixture: and being doped with 0.78 % of S-811 shows the following switching parameters: V 10 1.73 V VgoΛ o 1.068 Example 6 A STN display as described in Example 1 containing a liquid crystalline medium with the following properties: S-N < -40° N-l +87° Δn 0.1407 consisting of an aehiral base mixture: and being doped with 0.79 % S-811 shows the following switching parameters: T^ 272 ms V 10 1.78 V VgoΛΛo 1.064 Exgmplg 7 A STN display as described in Example 1 containing a liquid crystalline medium with the following properties: N-l 90.7° Δn 0.1431 consisting of an aehiral base mixture: and being doped with 0.61 % S-811 shows the following switching parameters: A STN display as described in Example 1 containing a liquid crystalline medium with the following properties: N-l +87.5° Δn 0.1411 consisting of an aehiral base mixture: and being doped with 0.61 % S-811 shows the following switching parameters: T & e 224 ms V 10 1.72 V VgoΛ o 1.081 Example 9 A STN display as described in Example 1 containing a liquid crystalline medium with the following properties: N-l +87° Δn 0.1429 consisting of an aehiral base mixture: CPTP-302 8.00 CPTP-303 8.00 PTP-20F 4.00 CCH-31 5.00 CCH-33 7.00 CCH-34 8.00 BCH-201 7.00 and being doped with 0.61 % S-811 shows the following switching parameters: A STN display as described in Example 1 containing a liquid crystalline medium with the following properties: N-l +87.5° Δn 0.1407 consisting of an aehiral base mixture: PCH-3 20.00 PCH-4 7.00 ME2N.F 4.00 ME3N.F 4.00 ME5N.F 4.00 CCP-20CF3 5.00 CCP-30CF3 5.00 CCP-40CF3 4.00 CPTP-301 5.00 CPTP-302 6.00 CPTP-303 5.00 PTP-20F 4.00 CCH-32 10.00 CCH-34 10.00 BCH-301 3.00 BCH-201 4.00 and being doped with 0.61 % S-811 shows the following switching parameters: A STN display as described in Example 1 containing a liquid crystalline medium with the following properties: N-l +85 Δn 0.1417 consisting of an aehiral base mixture: PCH-3 20.00 PCH-4 9.00 ME2N.F 2.00 , ME3N.F 2.00 CCP-20CF3 5.00 CCP-30CF3 5.00 CCP-40CF3 4.00 CPTP-301 5.00 CPTP-302 5.00 CPTP-303 5.00 PTP-20F 4.00 K6 7.00 CCH-32 10.00 CCH-34 10.00 BCH-301 2.00 BCH-201 5.00 and being doped with 0.61 % S-811 shows the following switching parameters: T^ 220 ms V 10 1.94 V Example 12 A STN display as described in Example 1 containing a liquid crystalline medium with the following properties: N-l +86° Δn 0.1427 consisting of an aehiral base mixture: PCH-3 25.00 ME2N.F 3.00 ME3N.F 3.00 ME5N.F 6.00 ME7N.F 5.00 CCP-20CF3 4.00 CCP-30CF3 4.00 CCP-40CF3 4.00 CPTP-301 5.00 CPTP-302 5.00 CPTP-303 5.00 PTP-20F 4.00 CCH-34 20.00 BCH-201 7.00 and being doped with 0.61 % S-811 shows the following switching parameters: A STN display as described in Example 1 containing a liquid crystalline medium with the following properties: N-l +84.5 o Δn 0.1386 consisting of an aehiral base mixture: PCH-3 27.00 PCH-4 4.00 PCH-302 5.00 CCP-20CF3 6.00 CCP-30CF3 5.00 CPTP-301 4.00 CPTP-302 5.00 CPTP-303 5.00 PTP-20F 5.00 K6 7.00 CCH-34 20.00 BCH-302 7.00 and being doped with 0.61 % S-81 1 shows the following switching parameters: A STN display as described in Example 1 containing a liquid crystalline medium with the following properties: N-l +88.5° Δn 0.140 consisting of an aehiral base mixture: PCH-3 22.00 PCH-4 6.00 ME2N.F 3.00 ME3N.F 3.00 ME5N.F 5.00 CCP-20CF3 5.00 CCP-30CF3 5.00 CCP-40CF3 4.00 CPTP-301 5.00 CPTP-302 6.00 CPTP-303 5.00 PTP-20F 4.00 CCH-32 10.00 CCH-34 10.00 BCH-301 4.00 BCH-302 3.00 and being doped with 0.61 % S-81 1 shows the following switching parameters: A STN display with the following parameters: contains a liquid crystalline medium with the following properties: S-N < -l4° N-l + 82° Δn 0.1346 consisting of an aehiral base material: PCH-3 18.00 PCH-4 7.00 PCH-5 6.00 ME-2N.F 3.00 ME-3N.F 4.00 ME-5N.F 3.00 B-10.FN 7.00 B-20.FN 7.00 CCP-20CF3 6.00 - 67 - CCP-30CF3 7.00 CCP-40CF3 6.00 CCP-50CF3 6.00 BCH-301 3.00 BCH-302 4.00 CCH-34 9.00 CCPC-33 4.00 and being doped with 0.61 % of S-811 shows the following switching properties: A STN display as described in Example 8 contains a medium with the following properties: 10 and being doped with 0.61 % of S-811 shows the following switching parameters: la*, 295 ms V 10 1.79 V 15 VgoΛΛo 1.067 This comparison clearly shows that with the aid of bieyclohexanyles of formula 11 and/or cyclohexylbiphenyl of formula 12 switching times can be considerably improved. 20. Example 16 A STN display as described in Example 1 containing a liquid crystalline medium with the following properties: 25 S-N < -15° N-l +71 ° Δn 0.1399 30 consisting of an aehiral base material PCH-3 25.00 PCH-4 14.00 PCH-302 20.00 35 PCH-304 6.00 - 69 - PTP-102 6.00 CPTP-301 4.00 CPTP-302 3.00 BCH-301 10.00 BCH-302 5.00 CCH-34 7.00 and being doped with S-811 shows the following switching properties: T^ 226 ms V 10 2.25 V VgoΛ/ 10 1.043 Comparative Example 2 A STN display as described in Example 16 containing a liquid crystalline medium with the following properties: S-N < -40° N-l +74° Δn 0.1383 consisting of an aehiral base material G9 10.00 PCH-3 24.00 PCH-5 5.00 PCH-302 16.00 CP-30CF3 5.00 ECCP-31 6.00 ECCP-32 5.00 ECCP-33 5.00 PTP- 102 6.00 PTP-201 6.00 BCH-32 6.00 BCH-52 6.00 and being doped with S-81 1 shows the following properties: T∞ 231 ms V 10 2.29 V VgoΛ o 1.052 Example 17 A STN display with the following parameters: twist angle 240° d 4.9 μm contains a liquid crystalline medium with the following parameters: N-l +86° ΔN +0.1749 consisting of an aehiral base mixture: K6 9.00 K9 8.00 K15 9.00 BCH-32 8.00 CCH-34 8.00 CCH-35 8.00 PCH-301 8.00 CCP-30CF3 5.00 CCP-40CF3 5.00 PTP-102 6.00 PTP-201 6.00 CPTP-301 5.00 CPTP-302 7.00 being doped with S-811 shows the following switching properties: A STN display as described in Example 17 contains a liquid crystalline medium with the following parameters: N-l +81° Δn +0.1719 consisting of an aehiral base mixture: PTP-201 4.00 CPTP-301 5.00 CPTP-302 7.00 being doped with S81 1 shows the following switching properties: T^ 98 ms V 10 2.24 V Example 19 Preparation of A mixture of 0.3 moles of 4-bromobenzonitrile, 0.33 moles of 2-fluoro-4- methoxyphenylboronic acid, 75 ml of toluene, 350 ml of ethanol, 490 ml of a 2m sodium carbonate solution and 9.1 g of tetrakis(triphenyl(phosphin)) palladium (O) is heated 3.5 hrs under reflux. After usual work-up and crystallization from ethanol the pure product is obtained, K 82 N (45.3) I. Analogously the following compounds are obtained: H,C ? 0- H o ) — < O >-CN K 77 N (49.3) 74 - Example 20 A STN display with the following parameters: contains a liquid crystalline medium with the following properties: S-N -40° N-l +88° Δn 0.1391 consisting of an aehiral base mixture: PCH-3 22.00 ME2N.F 3.00 ME3N.F 3.00 B-10.FN 6.00 B-20.FN 5.00 PCH-302 15.00 CCH-34 3.00 ECCP-3F.F 4.00 ECCP-5F.F 4.00 CCP-20CF3 4.00 CCP-30CF3 4.00 CCP-40CF3 4.00 CPTP-301 5.00 CPTP-302 5.00 ECCP-31 4.00 ECCP-32 4.00 ECCP-33 4.00 CCPC-33 2.00 and being doped with 0.61 % of S-81 1 shows the following switching parameters: T^ 289 ms V 10 1.91 V VgoΛ o 1.049 Example 21 A STN display as described in Example 20 containing a liquid crystalline medium with the following parameters: S-N < 0° N-l +89° Δn 0.1401 consisting of an aehiral base mixture: being doped with 0.61 % of S-811 shows the following switching parameters: Tae 266 ms V 10 1.83 V Example 22 A STN display as described in Example 20 containing a liquid crystalline medium with the following properties: S-N < +20° N-l +89° Δn 0.1424 consisting of an aehiral base mixture: PCH-3 22.00 B-10.FN 7.00 B-20.FN 7.00 B-30.FN 5.00 B-40.FN 5.00 CCH-34 16.00 CCP-20CF3 7.00 CCP-30CF3 7.00 CCP-40CF3 6.00 CPTP-301 4.00 CPTP-302 4.00 ECCP-31 4.00 ECCP-32 4.00 CCPC-33 2.00 being doped with 0.61 % of S-811 shows the following switching parameters: T a * 279 ms V 10 1.88 V VgoΛΛo 1.052 Example 23 A STN display as described in Example 20 containing a liquid crystalline medium with the following properties: S-N < -40° N-l +90° Δn 0.1403 consisting of an aehiral base mixture: and being doped with 0.61 % of S-81 1 shows the following switching parameters: T^ 295 ms V 10 1.82 V VgoΛΛo 1.050 Comparative Example 3 A STN display as described in Example 20 contains a liquid crystalline medium with the following parameters S-N -30° N-l 88° Δn 0.1398 consisting of and being doped with 0.61 % of S-81 1 shows the following switching parameters: Tae 295 ms V 10 1.79 V VQOΛ Q 1.067 This comparison clearly shows that the replacement of cyanophenyl benzoate (ME-nN.F) compounds by laterally fluorinated cyanobiphenyls B-nO.FN yields better steepness and/or shorter switching times. Example 24 A STN display with the following parameters: contains a medium with the following properties: S-N < -15° N-l +74° Δn 0.1405 consisting of an aehiral base material: PCH-3 23.00 PCH-302 20.00 PCH-304 8.00 PTP-102 4.50 CPTP-301 6.00 CPTP-302 6.00 CPTP-303 5.00 B-10.FN 7.00 CCH-32 3.50 CCH-34 12.00 CCP-30CF3 5.00 and being doped with 0.85 % of S-811 shows the following switching properties: T^ 223 ms V 10 2.28 V Comparative Example 4 A STN display as described in Example 24 contains a medium with the following properties: S-N < -40° N-l +74° Δn 0.1383 consisting of an aehiral base material: G9 10.00 PCH-3 24.00 PCH-5 5.00 PCH-302 16.00 CP-30CF3 5.00 ECCP-31 6.00 ECCP-32 5.00 ECCP-33 5.00 PTP-102 6.00 PTP-201 6.00 BCH-32 6.00 BCH-52 6.00 and being doped with 0.86 % of S-811 shows the following switching properties: T^ 238 ms V 10 2.29 V This comparison clearly shows that the switching times and the steepness can be improved with the aid of B-nO.FN. Example 25 A STN display as described in Example 20 contains a mixture with the following properties: S-N < 0° K-l +84° Δn 0.1293 consisting of an aehiral base material and being doped with 0.75 % of S-811 shows the following switching properties: T^ 310 ms V 10 1.83 V Vgo/V 10 1.049 Comparative Example 5 A STN display as described in Example 25 contains a medium with the following properties S-N < -40 K-l +84° Δn 0.1287 consisting of an aehiral base material: and being doped with 0.73 % of S-811 shows the following switching properties: A STN display as described in Example 20 contains a medium with the following properties: K-l +74.5° Δn 0.1425 consisting of an aehiral base material: ME2N.F 3.00 ME3N.F 5.00 ME5N.F 15.00 ME7N.F 5.00 HP-3N.F 4.00 PCH-3 19.00 PCH-302 4.00 CCPC-33 5.00 CPTP-301 5.00 CPTP-302 5.00 CBC-33F 2.00 CCH-32 9.00 CCH-34 12.00 B-10.FN 3.00 B-20.FN 4.00 and being doped with S-811 shows the following switching parameters: • ave 313 ms Vio 1.33 V Vgo/V 10 1.068 Comparative Example 6 A STN display as described in Example 26 contains a medium with the following properties: K-l +74.5° Δn 0.1460 consisting of an aehiral base material: ME2N.F 3.00 ME3N.F 5.00 ME5N.F 10.00 HP-3N.F 4.00 HP-4N.F 4.00 PYP-5F 8.00 K6 8.00 PCH-301 10.00 PCH-302 10.00 CCH-303 14.00 ECCP- 4.00 CPTP-301 4.00 CPTP-302 3.00 CPTP-303 5.00 CBC-33F 4.00 CBC-53F 4.00 and being doped with S-811 shows the following switching parameters: T^ 290 V 10 1.46 V VgoΛΛo 1.078 Example 27 A STN display as describes in Example 20 contains a medium with the following properties: K-l +110.0° Δn 0.1263 consisting of an aehiral base material: B-10.NF 7.00 B-20.NF 6.00 ME2N 3.00 ME2N.F 2.00 ME3N.F 3.00 PCH-302 11.00 CCH-301 5.00 ECCP-3F.F 10.00 ECCP-5F.F 10.00 CCP-20CF3 6.00 CCP-30CF3 6.00 CCP-40CF3 6.00 CCP-50CF3 6.00 ECCP-3 9.00 CBC-33F 5.00 CBC-53F 5.00 and being doped withe S-811 shows the following switching properties: V 10 2.10 V VgoΛ o 1.052 Example 28 A STN display with the following parameters: contains a liquid crystalline medium with the following properties: S-N < -30° N-l +78° Δn 0.1614 consisting of an aehiral base mixture: PCH-2 16.00 ME2N.F 3.00 PCH-301 7.00 K 6 5.00 K 9 5.00 PYP-5F 10.00 CCH-34 15.00 CP-33F 5.00 CPTP-301 6.00 CPTP-302 6.00 CPTP-303 6.00 CPTP-30CF3 6.00 CPTP-50CF3 6.00 PTP-201 4.00 and being doped with 0.95 % of S-81 1 shows the following switching parameters: A STN display as described in Example 28 containing a liquid crystalline medium with the following parameters: S-N < -30° N-l +79° Δn 0.1635 consisting of an aehiral base mixture: being doped with 0.97 % of S-81 1 shows the following switching parameters: A STN display as described in Example 28 containing a liquid crystalline medium with the following properties: S-N < -40 o N-l +108 o Δn 0.1450 consisting of an aehiral base mixture: PCH-2 13.0 PCH-3 18.0 PCH-4 4.0 PCH-5 4.0 CCH-34 15.0 CPTP-301 7.0 CPTP-302 7.0 CPTP-303 7.0 BCH-32 11.0 CP-33F 7.0 CP-35F 7.0 being doped with 0.92 % of S-811 shows the following switching parameters: A STN display as described in Example 28 and a cell gap of 5.9 μm containing a liquid crystalline medium with the following properties: S-N < -40 o N-l +110° Δn 0.1451 consisting of an aehiral base mixture: PCH-2 6.0 PCH-3 20.00 PCH-5 6.0 ME2N.F 4.0 ME3N.F 3.0 CCH-34 16.0 CPTP-301 6.0 CPTP-302 6.0 CPTP-303 6.0 BCH-32 11.0 CP-33F 7.0 CP-35F 7.0 CBC-33 2.0 and being doped with 0.92 % of S-81 1 shows the following switching parameters: Ta v e 250 ms V 10 2.12 V V 9 oΛ 10 1.054 Example 32 A STN display as described in Example 28 and a cell gap of 6.3 μm containing a liquid crystalline medium with the following properties: S-N < -40° N-l +108° Δn 0.1350 consisting of an aehiral base mixture: PCH-2 „ 13.0 PCH-3 18.0 PCH-4 4.0 PCH-5 4.0 CCH-34 12.0 CPTP-301 5.0 CPTP-302 5.0 CPTP-303 6.0 BCH-32 9.0 CP-33F 8.0 CP-35F 8.0 CP-55F 8.0 and being doped with 0.85 % of S-81 1 shows the following switching parameters: Ta*> 340 ms V 10 2.43 V VgoΛ o 1.098 Example 33 A STN display as described in Example 28 and a cell gap of 6.3 μm containing a liquid crystalline medium with the following properties: S-N < -20° N-l +113° Δn 0.1357 consisting of an aehiral base mixture: PCH-2 6.0 PCH-3 20.0 PCH-5 6.0 ME2N.F 4.0 ME3N.F 3.0 CCH-34 17.0 CPTP-301 3.0 CPTP-302 4.0 CPTP-303 3.0 BCH-32 11.0 CP-33F 7.0 CP-35F 7.0 CBC-33 5.0 CBC-53 4.0 and being doped with 0.86 % S-81 1 shows the following switching parameters: J ae 295 ms V 10 2.15 V VgoΛ o 1.066 Example 34 A STN display as described in Example 28 and a cell gap of 6.3 μm containing a liquid crystalline medium with the following properties: SN < -20 o N-l +110° Δn 0.1350 consisting of an aehiral base mixture: PCH-2 6.0 PCH-3 20.0 PCH-4 7.0 PCH-5 7.0 ME2N.F 2.0 ME3N.F 2.0 CCH-34 15.0 CPTP-301 3.0 CPTP-302 3.0 CPTP-303 4.0 BCH-32 8.0 CP-33F 6.0 CP-35F 6.0 CBC-33 3.0 CBC-53 4.0 CBC-55 4.0 and being doped with 0.86 % S-811 shows the following switching parameters: Ta^e 310 ms V 10 2.20 V Example 35 A STN display as described in Example 28 and a cell gap of 6.3 μm containing a liquid crystalline medium with the following properties: S-N < -40° N-l +110° Δn 0.1354 consisting of an aehiral base mixture: PCH-2 6.0 PCH-3 20.0 PCH-5 6.0 ME2N.F 4.0 ME3N.F 3.0 PCH-301 5.0 CCH-34 6.0 CPTP-301 6.0 CPTP-302 6.0 CPTP-303 6.0 CP-33F 7.0 CP-35F 7.0 CCPC-33 4.0 CCPC-35 4.0 and being doped with 0.86 % S-811 shows the following switching parameters: T a e 320 ms V 10 2.20 V Comparative Example 7 A STN display as described in Example 35 contains a medium with the following properties: S-N -40° N-l +112° Δn 0.1354 consisting of PCH-302 . 26.0 ME2N.F 3.0 ME3N.F 3.0 ME5N.F 7.0 ME7N.F 6.0 ECCP-31 5.0 ECCP-32 5.0 ECCP-33 5.0 ECCP-3 9.0 ECCP-5 9.0 ECCP-3F.F 8.0 CBC-33 3.0 CBC-53 3.0 CPTP-301 4.0 CPTP-302 4.0 and being doped with 0.86 % of S-811 shows the following switching parameters: This comparison clearly shows that with the aid of bieyclohexanyles of formula 11 and/or phenyl bicyclohexylcarboxylates of formula 12 switching times can be considerably improved. Example 36 A STN display as described in Example 28 containing a liquid crystalline medium with the following properties: consisting of an aehiral base material and being doped with S-811 shows the following switching properties: ' a* 136 ms V 9θ /V 10 1.076 Comparative Example 8 A STN display as described in Example 28 containing a liquid crystalline medium with the following properties: S-N < -30° N-l +80° Δn 0.1627 consisting of an aehiral base material and being doped with S-811 shows the following properties: ' awe 145 ms Comparative Example 9 A STN display as described in Example 28 containing a liquid crystalline medium with S-N < -30° N-l +80° Δn 0.1615 consisting of an aehiral base material and being doped with S-811 shows the following properties: Taw 130 ms V 10 2.03 V VgoΛΛo 1.060 Example 37 A STN display as described in Example 28 having d = 8 μm containing a liquid crystalline medium with S-N < -30 °C N-l +85 °C Δn 0.1096 consisting of an aehiral base material PCH-3 22.0 % P.CH-4 4.0 % PCH-301 7.0 % ME2N.F 2.0 % ME3N.F 3.0 % CCH-34 15.0 % PYP-31 8.0 % CCP-20CF3 5.0 % CCP-30CF3 6.0 % CCP-40CF3 3.0 % CP-33F 6.0 % CP-35F 5.0 % BCH-32 8.0 % CCPC-33 3.0 % CCPC-34 3.0 % and being doped with S-811 shows the following switching properties: T^ 310 ms V 10 2.06 V VgoΛ o 1.095 Example 38 A STN display as described in Example 1 containing a liquid crystalline medium with S-N < -15 °C N-l 85.4 °C Δn 0.1425 consisting of an aehiral base material PCH-3 21 % PCH-5 15 % PCH-302 23 % K6 4 % BCH-32 7 % ECCP-31 5 % ECCP-32 5 % CPTP-301 5 % CPTP-302 5 % CPTP-303 4 % CCP-V-OT 6 % and being doped with S-811 shows the following switching properties: A STN diplay as described in Example 1 containing a liquid crystalline medium with S-N < -15 °C - 101 - N-l 87.3 °C Δn 0.1435 consisting of an aehiral base material PCH-3 21 % PCH-5 15 % PCH-302 23 % K6 4 % BCH-32 7 % ECCP-31 5 % ECCP-32 5 % CPTP-301 5 % CPTP-302 5 % CPTP-303 4 % CCP-1V-OT 6 % and being doped with S-811 shows the following switching properties: Jaei 287 ms V 10 : 2.33 V VgoΛ o: 1.029 Example 40 A STN display as described in Example 1 containing a liquid crystalline medium with S-N < -15 °C N-l 86.5 °C Δn 0.1425 consisting of an aehiral base material - 102 and being doped with S-811 shows the following switching properties: T a *: 280 ms V 10 : 2.33 V Comparative Example 10 A STN display as described in Example 1 containing a liquid crystalline medium with S-N < -15 °C N-l 85.4 °C Δn 0.1415 consisting of an aehiral base material PCH-3 21 % PCH-5 15 % PCH-302 23 % K6 4 % BCH-32 7 % ECCP-31 5 % 103 - ECCP-32 CPTP-301 CPTP-302 CCP-20CF3 CCP-40CF3 and being doped with S-811 shows the following switching properties: T a ^: 245 ms V 10 : 2.35 V VgoΛ o: 1.043 This comparison shows that the replacement of CCP-nOCF3 by CCP-nV-OT or CCP-nE30CF3 (Example 38-40) considerably improves the electro-optic steeptness (Vgo V 10 ). Example 41 A STN display as described in Example 1 containing a liquid crystalline medium with S-N < -15 °C N-l 89.1 °C Δn 0.1440 consisting of an aehiral base material PCH-3 PCH-5 PCH-302 K6 BCH-32 ECCP-32 CPTP-301 104 - and being doped with S-811 shows the following switching properties: A STN display as described in Example 1 containing a liquid crystalline medium with N-l +78 °C Δn 0.1411 consisting of an aehiral base material and being doped with S-811 shows the following switching properties: T a ^: 188 ms V 10 : 2.26 V Vgo/Vio: 1.040 Example 43 A STN display as described in Example 1 containing a liquid crystalline medium with N-l 76 °C Δn 0.1451 consisting of an aehiral base material PCH-3 23.00% PCH-302 20.00% PCH-304 6.00% CCH-303 12.00 % PTP- 102 5.00 % CPTP-301 6.00 % O CPTP-302 6.00 % CPTP-303 5.00 % B-10.FN 7.00 % ECCP-31 4.00 % CCP-30CF3 6.00 % and being doped with S-811 shows the following switching properties: A STN display as described in Example 17 containing a liquid crystalline medium with N-l 85 °C Δn 0.1726 consisting of an aehiral base material PCH-2 11.00 % ME2N 4.50 % K6 8.00 % K9 8.00 % PYP-5F 2.00 % PYP-32 2.00 % PCH-301 6.50 % PTP-102 4.50 % PTP-201 6.00 % ECCP-31 7.00 % o ECCP-32 3.00 % ECCP-3F 7.50 % Ό CPTP-301 6.00 % CPTP-302 6.50 % CPTP-303 5.00 % CCH-35 12.50 % and being doped with S-811 shows the following switching properties: Ta«: 116 ms Vι 0 : 2.09 V VgoΛ o: 1.077 Example 45 A STN display as described in Example 17 containing a liquid crystalline medium with N-l 95 °C Δn 0.1705 consisting of an aehiral base material ME2N.F 2.00 % ME3N.F 3.00 % ME4N.F 5.00 % PCH-3 21.00 % PCH-302 15.00 % PTP-102 6.00 % PTP-201 5.00 % PTP-20F 2.00 % ECCP-3F 3.00 % CPTP-301 5.00 % CPTP-302 6.00 % CPTP-303 5.00 % BCH-32 5.00 % CBC-33 3.00 % CBC-33F 4.00 % CCH-35 10.00 % and being doped with S-811 shows the following switching properties: T a« >: 123 ms Vι 0 : 2.07 V VgoΛΛo: 1.052 Example 46 A STN display as described in Example 17 containing a liquid crystalline medium with N-l 82 °C Δn 0.1745 consisting of an aehiral base material and being doped with S-811 shows the following switching properties: 80 ms Vio: 2.47 V Example 47 A STN display as described in Example 17 containing a liquid crystalline medium with N-l 81 °C Δn 0.1749 consisting of an aehiral base material - 109 and being doped with S-811 shows the following switching properties: A STN display as described in Example 17 containing a liquid crystalline medium with N-l 78 °C Δn 0.1722 consisting of an aehiral base material K6 3.00 % K9 8.00 % CCH-34 10.00 % PCH-301 13.00 % and being doped with S-811 shows the following switching properties: A STN display as described in Example 17 containing a liquid crystalline medium with N-l 84 °C Δn 0.1733 consisting of an aehiral base material K6 8.00 % K9 6.00 % PCH-3 10.00 % BCH-32 5.00 % CCH-34 10.00 % PCH-301 11.00 % PTP-20F 6.00 % PTP-40F 6.00 % - 11 1 - CCP-20CF3 4.00 % CCP-30CF3 5.00 % CCP-40CF3 4.00 % CCP-50CF3 5.00 % PTP- 102 4.00 % PTP-201 4.00 % CPTP-301 5.00 % CPTP-302 7.00 % and being doped with S-811 shows the following switching properties: V 10 : 2.21 V Example 50 A STN display as described in Example 1 containing a liquid crystalline medium with N-l 101 °C Δn 0.1407 consisting of an aehiral base material PCH-3 15.00 % ME2N.F 2.20 % ME3N.F 3.30 % ME4N.F 4.00 % PCH-302 7.50 % CCH-35 6.50 % ECCP-3 5.00 % ECCP-3F 12.00 % ECCP-5F 6.00 % 1 12 BCH-32 3.00 % BCH-2F.F 10.00 % BCH-3F.F 9.00 % PTP- 102 2.00 % PTP-201 2.50 % CPTP-301 5.00 % CBC-33F 4.00 % CBC-53F 3.00 % and being doped with S-811 shows the following switching properties: A STN display as described in Example 1 having a cell group of 5.6 μm containing a liquid crystalline medium with N-l 109°C Δn 0.1523 consisting of an aehiral base material PTP- 102 2.00 % o CCH-35 5.00 % CPTP-301 6.00 % CPTP-302 7.00 % CPTP-303 6.00 % CBC-33 2.00 % BCH-32 1.00 % and being doped with S-811 shows the following switching properties: Ta^: 226 ms V 10 : 2.07 V VgoΛ/io: 1.063 Example 52 A STN display as described in Example 51 containing a liquid crystalline medium with N-l 111 °C Δn 0.1523 consisting of an aehiral base material ME2N.F 3.00 % K6 5.00 % K9 5.00 % PCH-3 21.00 % PCH-4 10.00 % CP-30CF3 10.00 % CP-50CF3 7.00 % CCP-30CF3 5.00 % PTP- 102 2.00 % CP-33 6.00 % CCH-35 8.00 % CBC-33 4.00 % CPTP-301 5.00 % CPTP-302 6.00 % CPTP-303 3.00 % and being doped with S-811 shows the following switching properties: T JM ,: 201 ms Vι 0 : 2.09 V VgoΛ o: 1.071 Example 53 A STN display as described in Example 51 containing a liquid crystalline medium with S-N < -30 C N-l 101 °C Δn 0.1527 consisting of an aehiral base material ME2N.F 3.00 % ME3N.F 4.00 % PCH-3 20.00 % PCH-5 15.00 % PCH-302 5.00 % CP-30CF3 9.00 % CP-50CF3 9.00 % CCP-30CF3 6.00 % PTP-102 3.00 % CCH-35 5.00 % CPTP-301 6.00 % CPTP-302 7.00 % CPTP-303 6.00 % CBC-33 2.00 % and being doped with S-811 shows the following switching properties: A STN display as described in Example 51 containing a liquid crystalline medium with N-l 109 °C Δn " 0.1520 consisting of an aehiral base material ME2N.F 3.00 % ME3N.F 4.00 % PCH-3 20.00 % PCH-5 15.00 % PCH-302 5.00 % CP-30CF3 9.00 % CP-50CF3 9.00 % CCP-30CF3 6.00 % PTP- 102 3.00 % CCH-34 5.00 % CPTP-301 6.00 % CPTP-302 7.00 % CPTP-303 6.00 % CBC-33 2.00 % and being doped with S-811 shows the following switching properties: Ta*,: 222 ms V 10 : 2.03 V Example 55 A STN display as described in Example 51 containing a liquid crystalline medium with N-l 110 °C Δn 0.1574 consisting of an aehiral base material ME2N.F 3.00 % ME3N.F 4.00 % PCH-3 18.00 % PCH-5 17.00 % PCH-302 3.00 % CP-30CF3 9.00 % CP-50CF3 9.00 % CCP-30CF3 6.00 % PTP- 102 3.00 % o CCH-34 5.00 % CPTP-301 6.00 % CPTP-302 6.00 % CPTP-303 6.00 % CBC-33 2.00 % and being doped with S-81 1 shows the following switching properties: Tae: 208 ms V 10 : 1.99 V Vgo/Vio: 1.060 Example 56 A STN display as described in Example 51 containing a liquid crystalline medium with S-N < -30 °C N-l 100 °C Δn 0.1497 consisting of an aehiral base material ME2N.F 3.00 % ME3N.F 4.00 % PCH-3 23.00 % o PCH-5 12.00 % PCH-302 8.00 % CP-30CF3 8.00 % CP-50CF3 8.00 % ECCP-3 5.00 % PTP-102 4.00 % CCH-35 8.00 % CPTP-301 6.00 % CPTP-302 6.00 % CPTP-303 5.00 % and being doped with S-811 shows the following switching properties: T^: 218 ms V 10 : 2.07 V V 9 o/V 10 : 1.048 Example 57 A STN display as described in Example 51 containing a liquid crystalline medium with N-l 110 °C Δn 0.1496 consisting of an aehiral base material ME2N.F 3.00 % ME3N.F 4.00 % PCH-3 17.00 % PCH-5 19.00 % PCH-302 4.00 % CP-30CF3 9.00 % CP-50CF3 9.00 % CCP-30CF3 6.00 % PTP- 102 2.00 % CCH-35 5.00 % CPTP-301 6.00 % CPTP-302 6.00 % CPTP-303 6.00 % CBC-33 2.00 % and being doped with S-811 shows the following switching properties: T aw 222 ms V 10 : 2.06 V Example 58 A STN display as described in Example 1 having d = 7.5 μm containing a liquid crystalline medium with N-l 81 °C Δn 0.11129 consisting of an aehiral base material PCH-3 22.00 % PCH-302 22.00 % K6 6.00 % CCH-35 8.00 % BCH-32 6.00 % CCP-20CF3 5.00 % CCP-30CF3 7.00 % CCP-40CF3 5.00 % CCP-50CF3 7.00 % CP-30CF3 5.00 % CP-50CF3 4.00 % CPTP-302 3.00 % and being doped with S-811 shows the following switching properties: Ta^: 226 ms V 10 : 2.32 V VQ O Λ O : 1.069 Example 59 A STN display as described in Example 58 containing a liquid crystalline medium with N-l 80 °C Δn 0.1120 consisting of an aehiral base material PCH-3 21.00 % PCH-302 22.00 % K6 7.00 % CCH-35 8.00 % BCH-32 4.00 % CCP-20CF3 6.00 % CCP-30CF3 7.00 % CCP-40CF3 6.00 % CCP-50CF3 7.00 % CP-30CF3 5.00 % CP-50CF3 4.00 % CPTP-302 3.00 % and being doped with S-811 shows the following switching properties: V 10 : 2.28 V VgoΛ o: 1.070 Example 6Q A STN display as described in Example 58 having d = 5.2 μm containing a liquid crystalline medium with N-l 86 °C Δn 0.1633 consisting of an aehiral base material and being doped with S-811 shows the following switching properties: T a *>: 139 ms V 10 : 2.29 V VgoΛ o: 1.052 Example 61 A STN display as described in Example 60 containing a liquid crystalline medium with N-l 85 °C Δn 0.1644 consisting of an aehiral base material and being doped with S-811 shows the following switching properties: V 10 : 2.28 V V ΘO /V ,: 1.057 Example 62 A STN display as described in Example 1 containing a liquid crystalline medium with N-l 85 °C Δn 0.1452 consisting of an aehiral base material PCH-3 26.00 % PCH-4 16.00 % PCH-5 4.00 % PCH-302 8.00 % BCH-32 5.00 % CCP-30CF3 4.00 % CCP-50CF3 3.00 % ECCP-2 4.00 % ECCP-3 3.00 % ECCP-2F.F 7.00 % PTP-20F 6.00 % CPTP-301 6.00 % CPTP-302 6.00 % CCH-35 2.00 % and being doped with S-811 shows the following switching properties: ' a«e: 277 ms Vι 0 : 2.05 V Example 63 A STN display as described in Example 1 containing a liquid crystalline medium with N-l 95 °C Δn 0.1447 consisting of an aehiral base material Example 64 A STN display as described in Example 51 containing a liquid crystalline medium with N-l 95 °C Δn 0.1548 consisting of an aehiral base material PCH-3 20.00 % PCH-302 16.00 % K6 7.00 % CCH-34 8.00 % BCH-32 6.00 % CCP-30CF3 5.00 % ECCP-32 2.00 % PTP-20F 6.00 % ECCP-2 7.00 % ECCP-2F.F 6.00 % CPTP-301 6.00 % CPTP-302 6.00 % CPTP-303 5.00 % and being doped with S-811 shows the following switching properties: Vι 0 : 2.39 V V 9 o/V 10 : 1.054 Example 65 A STN display as described in Example 1 with a cell gap of 6.56 μm containing a liquid crystalline medium with N-l +80 °C Δn 0.1295 consisting of an aehiral base material PCH-2 18.0 % PCH-3 26.0 % ME-2N.F 2.0 % CCH-34 5.0 % PTP- 102 5.0 % PTP-201 6.0 % BCH-32 5.0 % CP-33F 5.0 % CCP-35F 5.00 % CCP-55F 4.0 % CBC-33 4.0 % CBC-53 4.0 % and being doped with S-811 shows the following switching properties: T^: 252 ms V 10 : 1.92 V VgoΛ o: 1.067 Example 66 A STN display as described in Example 17 containing a liquid crystalline medium with N-l +94 °C Δn 0.1897 consisting of an aehiral base material and being doped with S-811 shows the following switching properties: T^: 73 ms V 10 : 2.47 V VsoΛ o: 1.113 Example 67 In A STN display disclosed as Example 1 of EP 0 366 985 having the following parameters: twist angle 180 tilt angle 1 o d • Δn 0.5 the liquid crystalline medium has been replaced by a medium in which 9.8 % of trans, trans-4-methoxy-4'-propylcyclohexyl-cyclohexan (CCH- 301) has been replaced by trans, trans-4-methyl-4'-propylcyclohexyl- cyclohexan (CCH-31). The properties of the resulting displays are compared in Table 1. Table 1 Mixture S-N K-l Vio awe This clearly shows that replacing only about 10 % of CCH-301 by about 10 % of CCH-31 yields an improvement of the switching time by about 10 % without impairing other important properties.

Claims: Patent claims 1. Supertwist liquid-crystal display containing two plane-parallel outer plates which, together with a frame, form a cell, a nematic liquid-crystal mixture of positive dielectric anisotropy which is present in the cell, electrode layers with superposed alignment layers on the insides of the outer plates, - a pitch angle between the longitudinal axis of the molecules at the surface of the outer plates and the outer plates of from about 1 degree to 30 degrees, and a twist angle of the liquid-crystal mixture in the cell from alignment layer to alignment layer with a value of between 100 and 600°, wherein the nematic liquid-crystal mixture a) comprises 30-90 % by weight of a liquid-crystalline component A, comprising one or more compounds having a dielectric anisotropy of more than +1.5; b) comprises 10-65 % by weight of a liquid-crystalline component f3, comprising one or more components having a dielectric anisotropy from -1.5 to +1.5; c) comprises 0-20 % by weight of a liquid-crystalline component C. comprising one or more compounds having a dielectric anisotropy of below -1.5, and d) comprises an optically active component D in such an amount that the ratio between the layer thickness (separation of the plane-parallel outer plates) and the natural pitch of the chiral nematic liquid-crystal mixture is from about 0.2 to 1.3 and the nematic liquid-crystal mixture has a nematic phase range of at least 60 °C, a viscosity of not more than 35 mPa.s and a dielectric anisotropy of at least +1 , the dielectric anisotropies of the compounds and the parameters based on the nematic liquid-crystal mixture being based on a temperature of 20 °C, characterized in that component B comprises at least one compound of formulae 11 and/or 12: wherein R3 and R 4 are each independently alkyl with 1 to 8 C atoms, and/or the component A comprises at least one compound of formulae 111 and/or 1111 wherein Ri is alkyl or alkoxy with 1 to 8 C atoms, wherein R2 is oxaalkyi, alkenyl with up to 8 C atoms, 2. Display according to Claim 1 , characterized in that component B comprises at least one compound of formulae 11 and/or 12 and component A contains compounds of the formulae II and III, wherein R is alkyl, alkoxy, oxaalkyi, alkenyl or alkenyloxy with up to 12 C atoms, C ) — are each independently U through Le are each independently H or F, Zi is -COO-, -CH 2 CH 2 - or a single bond, Z2 is -COO-, -CH 2 CH 2 -, -C≡C or a single bond, Q is CF 2 , OCF 2 , CFH, OCFH or a single bond, Y is F or Cl, m is 1 or 2, and n isOorl. Display according to Claim 1 or 2 characterized in that component A contains at least one compound selected from the formulae lla to lid andlllatolllf: Q wherein R, U, L3 and Q have the meaning given. 4. Display according to at least one of Claims 1 to 3, characterized in that component B contains one or more compounds selected from the group comprising IV to V: in which Rs and Re have the meaning given for R and — A 5 and U have the meaning given for formulae II or III, - 134 - Z3 is -COO-, -CH 2 CH 2 -, -CH=CH- or a single bond, Z 4 is -COO- or a single bond. 5. Display according to at least one of the Claims 1 to 6, characterized in that component B contains one or more compounds of formula 11a: wherein 0 and p each are integers between 0 and 7 and the sum of 0 + p is an integer between 1 and 7. 6. Display according to at least one of the Claims 1 to 5, characterized 5 in that component B contains one or more compounds of formula I2a: 0 in which q and v are each an integer between 0 and 7 in particular 0 and 3, and the sum of q + v is an integer between 0 and 7, in particular 0 and 3. ς 7. Display according to at least one of Claims 1 to 9, characterized in that component B contains one or more compounds selected from the group comprising X to XII: 5 in which R9 and Rio have the meaning given for R. 8. Display according to at least one of Claims 1 to 10, characterized in that component A contains one or more compounds of the formula T1 b in which Rn is n is an integer from 1 to 15, L3 through Le are each, independently of one another, H or F, and X is F, Cl or OCF 3 . 9. Display according to Claim 10 or 11 characterized in that the nematic mixture contains 5-25 % of one or more compounds of formula 11 , 20-35 % of two or more compounds selected from the formulae X, XI, XII and T1 b, and 10-30 % of two or more compounds of formula lla. 10. Liquid-crystal mixture of the composition defined in one of Claims 2 to 9. 11. Use of compounds of formulae 11 , 12, 111 and/ 1111 wherein Ri, R2, R3 and R 4 have the meaning given for the improvement of the switching times and/or the electro-optic steepness of STN-displays. 12. Compounds of formula I2a, wherein the sum of q + v is 0 or 1. 13. 2'-Fluoro-4-cyano biphenyl of formula 111a wherein Qi is O, CH 2 or a single bond.

Inventors: BREMER MATTHIAS, ICHINOSE HIDEO, JUNGE MICHAEL, KOJIMA AKIHIRO, NUMATA HIROSHI, PAUSCH AXEL, REIFFENRATH VOLKER, RIEGER BERNHARD, SAWADA ATSUSI, TARUMI KAZUAKI, WEBER GEORG, BREMER, MATTHIAS, ICHINOSE, HIDEO, JUNGE, MICHAEL, KOJIMA, AKIHIRO, NUMATA, HIROSHI, PAUSCH, AXEL, REIFFENRATH, VOLKER, RIEGER, BERNHARD, SAWADA, ATSUSI, TARUMI, KAZUAKI, WEBER, GEORG
Applicants: BREMER MATTHIAS, ICHINOSE HIDEO, JUNGE MICHAEL, KOJIMA AKIHIRO, MERCK PATENT GMBH, NUMATA HIROSHI, PAUSCH AXEL, REIFFENRATH VOLKER, RIEGER BERNHARD, SAWADA ATSUSI, TARUMI KAZUAKI, WEBER GEORG, BREMER, MATTHIAS, ICHINOSE, HIDEO, JUNGE, MICHAEL, KOJIMA, AKIHIRO, NUMATA, HIROSHI, PAUSCH, AXEL, REIFFENRATH, VOLKER, RIEGER, BERNHARD, SAWADA, ATSUSI, TARUMI, KAZUAKI, WEBER, GEORG
Application year: 1994
Main classification: C09K19
IPC codes: C07C255, C09K19, G02F1